When the iphone first launched on at&t it had the same restriction. The problem I had was that when using data (which I do a lot) incoming phone calls would go straight to voicemail. No idea if Verizon works the same way, but it was incredibly annoying at the time.
That's because GPRS/EDGE baseband doesn't support simultaneous voice+data, because there's only one transceiver.
Not true. If the GPRS/EDGE device supports Dual Transfer Mode (DTM, some people call it class A although it's not 100% equivalent), then the device can have a simultaneous CS voice call and GPRS/EDGE data transfer with a single tranceiver. This naturally requires network support.
For example, Vodafone UK has DTM support in its 2G network. Also, several devices from several vendors support DTM aswell (e.g. most if not all Nokia 2G/3G phones).
So, it's really not a matter of the devices, but network support. Not many carriers talk about this, which is understandable as it'd be making their own (lack of) service visible...
Yes, people don't realize that UMTS phones have multiple radios. Its not magic to support both voice and data on them. A future LTE enabled iPhone will likely do it too, since it will have two radios (one for 850/1900Mhz CDMA2000 voice/3G EVDO data and one for 700Mhz LTE 4G data)
I'd say most of UMTS phones do not have multiple radios (if by this it is meant that the device can simultaneously use services from more than one cellular system).
in UMTS (WCDMA) actually the device can operate several radio bearers (RAB's) of which one can operate CS services such as speech and others PS services i.e. data transfer over WCDMA "basic" channels or over HSPA channels. This is a built-in feature of the UMTS system.
My understanding of the Verzion iPhone version is such that data services are run over LTE (if available) and voice calls are placed over the CDMA 1xRTT system. And, during a voice call, data transfer is not possible (LTE is dormant/turned off). At least according to (http://voiceoverlte.typepad.com/voice-and-sms-over-lte/2011/01/verizon-ltes-phones-still-no-voice-over-lte.html) this would be the case. I admit I'm not too familiar with the CDMA stuff.
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a correction to above... Naturally the Verizon iPhone does not have LTE. Instead it should say EVDO for data data.
That's because GPRS/EDGE baseband doesn't support simultaneous voice+data, because there's only one transceiver.
Not true. If the GPRS/EDGE device supports Dual Transfer Mode (DTM, some people call it class A although it's not 100% equivalent), then the device can have a simultaneous CS voice call and GPRS/EDGE data transfer with a single tranceiver. This naturally requires network support.
For example, Vodafone UK has DTM support in its 2G network. Also, several devices from several vendors support DTM aswell (e.g. most if not all Nokia 2G/3G phones).
Ref:
http://en.wikipedia.org/wiki/Dual_Transfer_Mode
http://www.3g.co.uk/3GForum/showpost.php?s=98d8f1a1b6657fe1b1940cacbc6ab2b7&p=436254&postcount=23
http://www.wirelessforums.org/uk-telecom-mobile/iphone-4-o2-vodafone-98366.html#post403161
So, it's really not a matter of the devices, but network support. Not many carriers talk about this, which is understandable as it'd be making their own (lack of) service visible...
Yes, people don't realize that UMTS phones have multiple radios. Its not magic to support both voice and data on them. A future LTE enabled iPhone will likely do it too, since it will have two radios (one for 850/1900Mhz CDMA2000 voice/3G EVDO data and one for 700Mhz LTE 4G data)
I'd say most of UMTS phones do not have multiple radios (if by this it is meant that the device can simultaneously use services from more than one cellular system). in UMTS (WCDMA) actually the device can operate several radio bearers (RAB's) of which one can operate CS services such as speech and others PS services i.e. data transfer over WCDMA "basic" channels or over HSPA channels. This is a built-in feature of the UMTS system. My understanding of the Verzion iPhone version is such that data services are run over LTE (if available) and voice calls are placed over the CDMA 1xRTT system. And, during a voice call, data transfer is not possible (LTE is dormant/turned off). At least according to (http://voiceoverlte.typepad.com/voice-and-sms-over-lte/2011/01/verizon-ltes-phones-still-no-voice-over-lte.html) this would be the case. I admit I'm not too familiar with the CDMA stuff.